The Collaborative International Dictionary of English v.0.48:

Oblige \O*blige"\ ([-o]*bl[imac]j"; 277), v. t. [imp. & p. p.
   Obliged ([-o]*bl[imac]jd"); p. pr. & vb. n. Obliging
   ([-o]*bl[imac]"j[i^]ng).] [OF. obligier, F. obliger, L.
   obligare; ob (see Ob-) + ligare to bind. See Ligament,
   and cf. Obligate.]
   1. To attach, as by a bond. [Obs.]
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            He had obliged all the senators and magistrates
            firmly to himself.                    --Bacon.
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   2. To constrain by physical, moral, or legal force; to put
      under obligation to do or forbear something.
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            The obliging power of the law is neither founded in,
            nor to be measured by, the rewards and punishments
            annexed to it.                        --South.
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            Religion obliges men to the practice of those
            virtues which conduce to the preservation of our
            health.                               --Tillotson.
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   3. To bind by some favor rendered; to place under a debt;
      hence, to do a favor to; to please; to gratify; to
      accommodate.
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            Thus man, by his own strength, to heaven would soar,
            And would not be obliged to God for more. --Dryden.
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            The gates before it are brass, and the whole much
            obliged to Pope Urban VIII.           --Evelyn.
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            I shall be more obliged to you than I can express.
                                                  --Mrs. E.
                                                  Montagu.
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WordNet (r) 3.0 (2006):

oblige
    v 1: force somebody to do something; "We compel all students to
         fill out this form" [syn: compel, oblige, obligate]
    2: bind by an obligation; cause to be indebted; "He's held by a
       contract"; "I'll hold you by your promise" [syn: oblige,
       bind, hold, obligate]
    3: provide a service or favor for someone; "We had to oblige
       him" [syn: oblige, accommodate] [ant: disoblige]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "oblige":
   accommodate, aid, assist, avail, benefit, bind, brook no denial,
   call for, cater to, coddle, coerce, commit, compel, concuss,
   constrain, contribute, convenience, cosset, demand, dictate,
   do a favor, do a service, do right by, exact, favor, force,
   give way to, gratify, help, humor, impose, indulge, insist upon,
   leave no option, make, make imperative, make incumbent,
   mollycoddle, necessitate, obligate, pamper, please, pledge, profit,
   require, saddle with, satisfy, serve, shotgun, show kindness to,
   spoil, take no denial, tie, treat well, yield to